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How to Create Humidity in A Grow Room?

Before you start reading: Are you interested in grow room humidifiers? If so, my favorite one is TaoTronics Cool Mist Humidifier with LED Display (Check for the best price on Amazon)

If you wish to grow healthy sprouts inside a grow room, you must ensure some of its basic needs. Air conditioning, lights, and humidity are important factors. Among these, humidity control is the one which is often gets overlooked.

Controlling humidity is very important for growing plants. It helps you to understand the resilience of your plants against mold or mildew. Plus, you can determine the drinking needs of your plants with the help of humidity.

Humidity in A Grow Room

How to Create Humidity in A Grow Room

Believe it or not, as an indoor gardener, I’ve seen many growers taking many risks about humidity control. So, you should focus on this fact to avoid a poor outcome in your quest for indoor gardening production.

Both the temperature and humidity are essential to control the grow room environment. The outdoor humidity can change the conditions of the grow room drastically. So, humidity is a must thing to address during every growing stage of plants.

It is essential to start controlling humidity at the early stages of the growth of plants. When they form a healthy root system, they can naturally handle a broad range of humidity.

However, various plants are affected in multiple ways by humidity. That’s why you should control the humidity of growing buds according to their kinds.

Fortunately, there aren’t many things to learn about humidity control in your growth. With a little effort, you can learn the ways to create humidity in a grow room. In this article, the many know-hows of gardening in a grow room have been explained. So, read it carefully and have a boost in production.

We recommend checking our guides about grow room humidifiers:

Importance of Humidity in the Grow Room

To properly grow the plants, we need to intake water consistently in each stage of growth. And the need for water changes concerning the humidity variations inside your grow room. When your room’s ambient humidity is high, your plants will pull less water from their roots.

In such situations, they fulfill the need for water by absorbing moisture from the air by their leaves. Reversely, in the case of low humidity, the plants pull a large amount of water from the roots.

The humidity variation changes the water requirements of your sprouts from time to time. So, the nutrients the plants need to intake are mostly dependent on the humidity. That means you should be the controller of humidity in your grow room.

Maintaining the humidity encourages healthy and leafy buds along with valorous growth. Yet, the growing of plants with Deep Water Culture at the time of vegetation can be a hard challenge.

When your plants start to make buds, manipulate the humidity of the plant’s growing areas. As a result, the plants will begin to produce resin in a large amount and prevent mold attack. Excessive humidity can be the worst nightmare of a grower. Relatively high humidity tends to cause bud rot or dense mold in young plants.

Additionally, increased humidity prevents the plants from inhaling CO2. And thus, it inhibits the efficient photosynthesis of plants.

Consequences of Low Humidity in Grow Room

The plants intake a lot of water by sucking up. But, a very little quantity of water is stored to build new cells. The majority of water passes simply through the plants. They are either sucked up by the plant roots or suffused in the vascular bodies. Finally, the water exits through the little holes in the leaves known as stomata.

The role of water in plants is primarily as a coolant similar to the engine of a car.

Low humidity in a grow room creates VPD or a high vapor pressure deficiency. Usually, the leaves of a plant are filled with moisture inside. The humidity inside the tiny air pockets of leaves is nearly 100%. That means the inside of the leaves is all wet, which is all good.

However, the plants breathe by exchanging gases with the air through tiny, little holes. These small breathing holes expose the plants to the outside world.

If the outer environment is dry, the plants have to fight the drying effect by sucking up lots of moisture. So, it has to work with lots of hardships to stay alive only.

Moreover, the low humidity effect of plants rises the chance of your plants being attacked by molds and mildew.

How to Control Humidity in the Grow Room?

Many new indoor gardeners in this area don’t understand how early all our efforts can go in vain. So, controlling your grow room climate should be at the top of your to-do list.

Here are a few key steps to control your grow room humidity. Have a look –

Set Up the Lighting System of Your Grow Room

Light is something that can be a crucial factor for the humidity change in your grow room. Usually, growers overlook this vital element while going to grow indoor plants. If the light amount passing through the room is higher, it contributes to increased heat in the room.

As a result, the humidity of the room may get excessively high. So, you should be concerned about this lighting issue to control the climate of your grow room. Think thoroughly to light the grow room so that the temperature of the room remains in your control.

Many indoor growers use LED Grow lights. Many are using metal halide lights and HPS lighting systems. They can increase heat and keep the room temperature beyond 20 degrees’ window. This is preferable to many growers.

Control The Grow Room Temperature

Usually, the grow room temperature lies within 20 degrees window due to light. This temperature is warm enough not to freeze the sprouts. Also, it is cool sufficiently to protect your plants from frying due to heat. So, keeping the light within this range, you should be worry regarding the cooling system of the room.

If you are growing your plants as a hobby in your room, using a window, AC is sufficient to cool the grow room atmosphere. It is unfortunate, sometimes using only a simple AC may not be efficient.

It is one of the worrying things when the growers go to scale up. When they go for growing plants on a large scale, such simple solutions may not work well. A window AC system is not suitable for large-scale growth. If your grow scale is large, you should look for a system like central air controlling in a home condition.

Keep The Air Movement Continuous through The Room

Keeping a continuous air movement through the grow room is a must. The air movement serves two purposes – it helps to prevent mold attack in the plants. Besides, it helps your plants to build up strong stems as well as branches.

The air circulation is also necessary for the transpiration process of the plants. Transpiration is the process by which the plants suck up water by their roots. Finally, the water is eliminated from the plant body by evaporation by the leaves. The air circulation in the grow room keeps the plant leaves moist.

So, the rate of evaporation decreases, and thus the attack of poisonous fungus and molds reduces. In short, air circulation is a must for maintaining the relative humidity in your grow room. Usually, oscillating fans are well enough to provide the continuity of air circulation.

Be Ready to Control the Humidity

To measure humidity, you can use a handheld sensor. These sensors can give accuracy within nearly five percent. For large indoor gardening operations, an electronic monitoring system is suitable. Electric humidifiers have both sensors and a recorder to record humidity.

People often overlook the humidity when they scale up for large growing operations. In such situations, they usually get confused about the moisture need of each plant. The amount of moisture necessary is quite a lot. In small planting systems, a small residential dehumidifier is enough to apply.

They are available at all hardware stores. But, when your operation is more extensive, a residential dehumidifier does not serve well. For those dozens of plants, an energy-efficient commercial dehumidifier can be efficient.

Control the Rate of CO2 in The Grow Room through Ventilation

Control the Rate of CO2 in The Grow Room through Ventilation

To control the humidity in the grow room, ventilation is one of the most practical methods. You can increase as well as decrease the grow room humidity with ease through this process. With the exchange of the amount of air through the room, humidity either increases or falls.

The growers usually do this by using an exhaust fan. To make the fan work efficiently, you have to add an intake hole to it or widen it. Thus, it will increase the amount of air movement throughout your grow room.

In some cases, you may need to add a light baffle surrounding the intake hole. By doing such, you can prevent the leakage of light and also allow sufficient flow of air.

Besides, you can use a hygrometer to power the fan to get more reliable efficiency and automation. Using a hygrometer is much more advantageous than using a thermostat with the fan. The plants need fresh C02 for photosynthesis rather than a constant amount of fresh air.

Many grow rooms either have constant CO2 systems or have no ventilation system. So, using a hygrometer controller can add extra benefits to the grow rooms.

The lack of ventilation and the enclosed area of the grow room cause a rise in relative humidity. So, you must use dehumidifiers and air conditioners to maintain the room temperature. Again, if the rate of metabolism of the plants increases, the transpiration rate rises. In that case, you don’t need to use a humidifier.

Grow Room Humidity Control Tips

Humidity is the environmental condition of an indoor garden, which is underrated mostly. You should keep an eye on it. During the plants’ vegetative growth period, it is good to maintain the range of humidity within 60 to 70%. The moisture within such ranges keeps an equilibrium condition due to water loss.

At the time of flowering stages, you should try to drop some of the humidity, and it is good to keep the range within 40% to 50%. Humidity in this range protects the tree from the formation of pathogens. It also ensures the free movement of water, nutrients, and minerals through the plant’s body.

Here are some safety measures and tips to control the grow room humidity:

  1. Keep in mind that when you turn off the lights in the grow room, the temperature drops. So, the relative humidity of the grow room increases. It will be very wise if you keep continuing the extraction even when the lights are turned off. Otherwise, you may invest some money on heaters so that the drop in the temperature doesn’t get too drastic. It prevents the deposition of water from the buds and provides a bearing land for pathogens.
  2. Inversely, when you turn on the lights of the grow room, the room temperature increases. This results in a drop in the relative humidity. To control humidity in such a case, using a timed humidifier will be the best decision. Try to invest in a humidifier with ultrasonic vibrations. It will release steam-free and cold water.
  3. Be sure to check the humidity levels and keep it higher in the vegetative growth period. Keep it lower at the time of the flowering stage.

Safety Measures

To keep the things moist in the grow room is essential. Make sure that the water you use is clean. If the water is not clean, the harmful bacteria present in the water can damage the health of your plants. It may cause a wide range of diseases to your plants as well as to your health.

Besides, maintain the plants in your grow room at a regular interval. While controlling the grow room humidity, keeping the plants is also essential.

Also, be careful to keep water trays or sponges close to the fans. Fans or other electric materials in the room may short circuit if they come in contact with water.

Read Here to know what types of humidifiers are best for indoor grow rooms.


Here are a few top frequently asked questions regarding the control of humidity-

What Should be the Target of Relative Humidity in a Grow Room?

To inhibit the mold growth and optimize the highest yield, the growers usually aim to get 50 to 60% humidity.hydroponic Tents FAQ

However, the target humidity varies depending on the scaling of the gardening process. In a commercial setting, the target aimed is often much higher than a residential setting.

Why Do You Need a Dehumidifier Even If You Have an A/C in a Grow Room?

Air conditioner can’t dehumidify efficiently after dehumidifying to a limited extent. Besides, you may face an overcooling condition. In that situation, the colder air can’t hold much water.

So, condensation of water starts to take place. Though the air conditioner releases water when it cools, humidity may rise due to the cooling.

We recommend checking our dehumidifier guide: Best Grow Tent Dehumidifiers Review & Buying Guide

Final Thought

Low relative humidity disturbs the plants to grow correctly. Controlling the humidity of the grow room is not very difficult. You can quickly learn the techniques to create and manage the humidity of your grow room.

In this article, the key steps about creating humidity in a grow room are discussed thoroughly. We are sure it will give you some boost for your harvesting!